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On MIM gun parts

Three little letters that often get the most derision from the gun community is MIM.

There are two types of mass production techniques that are similar and are often confused.  Powder Metallurgy (PM) and Metal Injection Molding (MIM).  Both methods use a metal powder mixed with a binder to fill a mold cavity with material.  The powder metal binder part that comes out is called a “green.”  The binder is removed from the green and the green is then sintered into a solid piece.

The differences in the process is what separates PM from MIM.

Powder size is one of the biggest differences.  PM powders are in the 50-100 micron range (0.002 – 0.004 in), while MIM powders are in the 2- 15 micron range (0.00008 – 0.0007 in).

The compaction of MIM is much higher than PM, using 40-50% binder in the green molding process, the material flows into the mold using processes borrowed from the plastic injection molding industry.

The debinding process in MIM is more involved, due to the higher volume percentage of binder.  It can be done by washing in water if is a water-soluble binder is used; solvent debinding using an organic solvent; or catalytic debinding, which uses an acidic vapor to dissolve the binding agent.  This converts the green to a brown part, which then goes to sinter.

In both PM and MIM, sintering is done at a minimum 70% of the melting temperature.  The higher starting porosity means that the MIM part will experience significantly more shrinkage during sinter.

PM parts will generally achieve a 92% max density.  MIM parts can achieve 95-98% max density, with much finer final porosity and higher dimensional tolerances during shrinkage.  MIM parts can then be subsequently heat treated in a process called hot isostatic pressing (HIP), in which the part is subject to extremely high temperature and pressure (30,000 psi) in an inert atmosphere furnace the further compacts the part to near 100% dense.

When complete, the general rule of thumb is that PM and MIM parts have the fractional percent of strength of full density parts, i.e., a steel MIM part this is 98% dense will have 98% the strength of the same part if it were machined from the same steel.  For static loads, this is accurate.  The microporosity in MIM does reduce the fracture toughness by about 20%.

All sorts of materials can be produced by MIM.  Common alloys include 4140, 4340, S7 tool steel, 9310, 8620, 17-4 PH (precipitation hardenable stainless steel), as well as custom blends.  It’s possible to alloy in situ using carbon, carbonyl iron, and other alloying elements to make modified alloys that respond well to MIM processing.

MIM parts then can be subsequently heat treated and finished using the same heat treats and finishes as machined parts, such as quench and temper, carbonizing, nitriding, ferritic nitrocarburizing (FNC), aging, etc., that apply to each alloy.

MIM has the advantage of being a relatively low-cost process to manufacture small, complex geometry parts, with high degrees of tolerancing.

This is perfect for the gun industry.

Decades ago, when MIM first started to be used in the firearms industry, it gained a poor reputation for quality.  This is common when a new technology enters the market.  However, in the last forty years, MIM technology and quality has increased substantially.

All of your favorite guns contain MIM parts, a lot of MIM parts, muzzle devices, sights, firing pins, disconnectors, extractors, ejectors, frames, and there are at least two pistols out there that have MIM barrels.

These are guns that have been tested by the design engineers for the companies that manufacture them  to tens of thousands of rounds.

With a property designed and manufactured MIM part, made from the appropriate material and given the correct heat treatment, a gun owner or shooter will never have a part fail because it was MIM and not machined.

The reflexive hatred of MIM parts is a vestigial belief that is almost half a century out of date from some early bad parts that were not made with modern MIM materials.  But that belief is used to get gun owners to shell out lots of money in machined aftermarket parts that they don’t need to buy.

Your factory MIM parts are fine.

I found Eversource’s problem

AWA is without power.

My lights have been flickering.

Yesterday I got this message from Eversourse, New Hampshire’s electric supplier.

 

I decided to give them a bit of my mind on Twitter about it.

Well… Eversourse got back to me.

Here is the relevant part of what they provided in the link.

 

A four to five year cycle?

This should be done annually the way FPL does for hurricane season.

They need more men with chainsaws.

The Gun Shaming Campaign Has Begun…. and it Went Dumb. (Music City Style)

I guess you well already know about the Gun Shaming campaign proposed by some gun control mouthpiece in Colorado. And here we have the confirmation and of all places, we got it locally in Nashville.:

NASHVILLE, Tenn. — Mayor John Cooper of Nashville, TN and 30 other members of Mayors Against Illegal Guns, a nonpartisan coalition of current and former mayors that is part of Everytown for Gun Safety, recently released new data about the manufacturers of recovered crime guns in their cities. According to the data provided by the city, Glock is the top manufacturer of crime guns recovered in Nashville. In 2021, four gun manufacturers accounted for over half of the recovered crime guns: Glock (21.1%), Smith & Wesson (13.5%), Taurus (13.0%), and Ruger (7.0%). A full list of cities that participated in the report is available below.

I’m particularly proud that MNPD Chief Drake and his team are taking on the crisis of stolen guns in vehicles and working hand in hand with community leaders to make our neighborhoods safer for everyone.”

NEW DATA: Analysis Reveals Nashville’s Top Manufacturer of Crime Guns – The Tennessee Tribune (tntribune.com)

I love the fact that Mayor Cooper (proud member of Felon Mayors Against Illegal Guns) brings out the Chief of Metro Nashville Police Department into this Public Relations attack against Glock because the official sidearm of MNPD is Glock. Will the Mayor of Nashville issue orders to immediately “De-Glock” the department and find substitute firearm that complies with the wishes of his boss, Michael Bloomberg? I propose they go with the Armatrix iP1 Smart Gun.

And in order to help the Mayor of Nashville, I propose a Police Glock Buyback where we set shop near where officers gather and offer them to trade their evil Glocks for $25 gift certificates, no questions asked. If they add three or more loaded magazines to the trade, they get upwards of $50 in gift cards.

Who is with me?

 

Nothing from AWA today

We’ve been without power here for almost 24 hours when you read this, unless power is restored over night.  Not a problem fur is.

The wood stove is doing a fine job of keeping the house warm. Wife is unhappy because she’s cold but everybody else is in short sleeves.

Last night we had homemade pasta that I made with some fancy chicken dish. Only requirement was it had to cook on top of the stove. My lady solved lack of oven by using a Dutch oven.

Hopefully I’ll have power and post later today.